1
GATE EE 2008
MCQ (Single Correct Answer)
+2
-0.6
A $$3$$-phase, $$440$$ $$V,$$ $$50$$ $$Hz,$$ $$4$$ pole, slip ring induction motor is feed from the rotor side through an auto transformer and the stator is connected to a variable resistance as shown in the figure. GATE EE 2008 Electrical Machines - Induction Machines Question 7 English

The motor is coupled to a $$220$$ $$V$$, separately excited $$d.c.$$ generator feeding power to fixed resistance of $$10\Omega .$$ Two watt-meter method is used to measure the input power to induction motor. The variable resistance is adjusted such that motor recorded
$${W_1} = 1800\,W,\,\,{W_2} = - 200\,W.$$

Neglecting all losses of both the machines, the $$dc$$ generator power output and the current through resistance $$\left( {{R_{ex}}} \right)$$ will respectively be

A
$$96$$ $$W,$$ $$3.10$$ $$A$$
B
$$120$$ $$W,$$ $$3.46$$ $$A$$
C
$$1504$$ $$W,$$ $$12.26$$ $$A$$
D
$$1880$$ $$W,$$ $$13.71$$ $$A$$
2
GATE EE 2008
MCQ (Single Correct Answer)
+1
-0.3
In a stepper motor, the detent torque means
A
minimum of the static torque with phase winding excited.
B
maximum of the static torque with phase winding excited.
C
minimum of the static torque with phase winding unexcited
D
maximum of the static torque with the phase winding unexcited
3
GATE EE 2008
MCQ (Single Correct Answer)
+1
-0.3
Distributed winding and short chording employed in AC machines will result in
A
increase in $$emf$$ and reduction in harmonics
B
reduction in $$emf$$ and increase in harmonics
C
increase in both $$emf$$ and harmonics
D
reduction in both $$emf$$ and harmonics
4
GATE EE 2008
MCQ (Single Correct Answer)
+2
-0.6
A synchronous motor is connected to an infinite bus at $$1.0p.u$$ voltage and draws $$0.6$$ $$pu$$ at unity power factor. Its synchronous reactance is $$1.0$$ $$pu$$ and resistance is negligible.

Keeping the excitation voltage same, the load on the motor is increased such that the motor current increases by $$20\% $$. The operating power factor will become

A
$$0.995$$ lagging
B
$$0.995$$ leading
C
$$0.791$$ lagging
D
$$0.848$$ leading
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